Gas delivery to plasma chambers for the purpose of plasma generation is an essential feature of many technologies. For example, it is employed in ion implantation, which has been a critical technology in semiconductor device manufacturing and is currently used for many processes including fabrication of the p-n junctions in transistors, particularly for CMOS devices such as memory and logic chips. By creating positively-charged ions using input gases, where the ions contain the dopant elements required for fabricating transistors in silicon substrates, ion implanters can selectively control both the energy (hence implantation depth) and ion current (hence dose) introduced into the transistor structures. Gas delivery to plasma chambers for the purpose of plasma generation is not limited to ion implantation, however. This feature may also be used in chemical-vapor deposition, plasma doping processes that do not require the extraction of an ion beam from the generated plasma, and other applications involving producing plasma from one or more input gases.
A shortcoming associated with most of today's gas delivery devices is that they do not distribute gases uniformly to the plasma chamber. Substantial uniformity in gas distribution is desirable for generating uniform plasma density in a plasma chamber and, in some cases, for extracting an ion beam having uniform beam current density from the plasma chamber. For example, in the context of ion implantation, wafer substrate sizes have become larger due to the recent demand for higher production volume. In turn, ion source sizes, especially the height of an ion source that is substantially parallel to the wafer substrate, are also larger to cover the wafer substrate. Enlargement of ion sources is especially important when there is no means to enlarge an ion beam extracted from the ion source during ion beam transport and/or to scan the wafer substrate during ion beam irradiation such that most of the surface of the wafer substrate is irradiated by the beam.
Even though some of the existing gas delivery devices may be able to distribute gases relative uniformly to a plasma chamber, these gas delivery devices cannot achieve the uniformity quickly, especially over a wide dimension (e.g., a longitudinal length) of the plasma chamber due to the large difference in the lengths of the gas distribution lines of the gas delivery devices. Hence, the existing gas delivery devices often incur a delay in gas delivery timing among different sections of the plasma chamber. Therefore, there is a need for an improved gas delivery device that is capable of quicker and more uniform gas distribution to an elongated plasma chamber over a wide delivery range.